Add day3

1 files changed, 36 insertions, 0 deletions

diff --git a/day3/src/main.rs b/day3/src/main.rs
new file mode 100644
index 0000000..aa7eda7
--- /dev/null
+++ b/day3/src/main.rs
@@ -0,0 +1,36 @@
+use std::fs::File;
+use std::io::prelude::*;
+use std::io::BufReader;
+
+fn main() -> Result<(), std::io::Error> {
+    let file = File::open("input.txt")?;
+    let reader = BufReader::new(&file);
+
+    let lines: Vec<_> = reader.lines().map(|x| x.unwrap()).collect::<Vec<String>>();
+    let mut bits: Vec<u32> = vec![0; lines[0].len()];
+    let half: u32 = (lines.len() / 2) as u32;
+    let mut gamma_string = String::new();
+    let mut epsilon_string = String::new();
+
+    for line in lines {
+        for (index, char) in line.chars().enumerate() {
+            bits[index] += char.to_digit(10).unwrap();
+        }
+    }
+
+    for bit in bits {
+        if bit >= half {
+            gamma_string.push('1');
+            epsilon_string.push('0');
+        } else {
+            gamma_string.push('0');
+            epsilon_string.push('1');
+        }
+    }
+    let gamma_rate = isize::from_str_radix(&gamma_string, 2).unwrap();
+    let epsilon_rate = isize::from_str_radix(&epsilon_string, 2).unwrap();
+
+    println!("{}", gamma_rate * epsilon_rate);
+
+    Ok(())
+}